I have a 55gal with, what was, three angelfish... and a couple live bearer tropical fish that managed to not get eaten or killed off.

This afternoon one of my Angelfish didn't look well. This particular Angelfish never ate much, thus hardly grew (I've had it for over a year) and I was always a little concerned about it. Usually it would peck food off the bottom, so i'd try to drop shrimp pellets for it. This week it didn't go after them. I thought something might've been wrong but did not see anything physically ailing it, and it was never very active anyway so I couldn't exactly tell if it was lethargic, lol. It usually stayed in a corner away from the other Angelfish.

This afternoon I noticed it appeared to be gasping -- breathing through it's mouth, really hard.

My other two angelfish are kind of violent right now because they've been breeding every couple of weeks (that's another story...) and they either kill or beat up all the fish that get near their corner, so I moved the sick angelfish out of that tank and put it in a very calm 25 gallon community tank.

It only lived for about an hour longer.

I don't understand what happened. I examined it after it died and didn't see anything physically wrong.
Is this an internal parasite sort of thing? contagious?
What should I do?

I'm concerned about my other angelfish, one of which I've had for years.

so I moved everything to a 25gallon (eep! 30 fish in a 25G! LOL)
Everything seems to be doing fine now, despite cramped quarters. I imagine it will only be a matter of time before my Angelfish decide to eat my mom's neons.

I tested the Alkalinity and, well, it was off-the-charts.
I thought it was because of the bucket I used to fill the tank so I drained it to the bottom.

Then my dad noticed our tap was weird (we have a water softener; does not control our ph though.).
As it turns out, the water dept just so happened to screw up today.

The 55G is filled back up, but PH is very high.
I put in a dose of PH-Down but made no improvement.

Just added another dose.

How long is it supposed to take for the PH to adjust? I've never had to use chemicals before to maintain a tank. Is this going to have to be a regular thing now that the water is totally messed up?

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edit:

Checked again this morning and ended up putting another dose Ph-down.

Now, After 3 doses, it's down to 7.4 from it's original 8.6, but I'm not sure if it's okay to have altered the water so much.

I'm thinking about buying Danios to test the water unless someone thinks a different breed would be better.